Carbon blacks are generally produced in a furnace-type reactor by pyrolyzing a hydrocarbon feedstock with hot combustion gases to produce combustion products containing particulate carbon black.
Carbon blacks may be utilized as pigments, fillers, reinforcing agents and for a variety of other applications. For example, carbon blacks are widely utilized as fillers and reinforcing agents in the compounding and preparation of rubber compositions for industrial rubber applications. Rubber compositions for industrial rubber applications include hoses, belts, electrical cable insulation and roofing compounds. Generally hoses, belts and electrical cable insulation are produced through extrusion techniques, i.e. the rubber composition is extruded through a die and then cooled or chemically hardened.
It is generally desirable in the production of rubber compositions to utilize carbon blacks which when incorporated will result in rubber compositions with reduced extrusion shrinkage. As is known to those of ordinary skill in the art, rubber compounds generally swell upon extrusion. This means that the cross sectional area of the extrudate is larger than the cross sectional area of the die opening through which it was forced. A low value for extrusion shrinkage correlates to a situation where compound swelling is reduced, and the extrudate cross sectional area is close to that of the die opening. Such compound behavior results in the compound having the intended size for the desired finished part.
Accordingly, an object of the present invention is the production of new carbon blacks which impart improved extrusion shrinkage properties to natural rubbers, synthetic rubbers and blends of natural and synthetic rubbers in which the carbon blacks are incorporated.
Another object of the present invention is new rubber compositions, advantageous for use in industrial rubber applications, incorporating the new carbon blacks which are characterized by having reduced extrusion shrinkage properties.
Other objects of the present invention will become apparent from the following description and the claims.